The choice of using an object versus a bed is entirely up to the mixer however there are a few things to keep in mind:
- Objects have no access natively to the Low Frequency Effects channel. In most circumstances this is not a consideration as the content that exists in the LFE should also exist in the main mix. In other words, don't rely on the LFE as the "bass channel".
- Bed channels map differently to different overhead speaker configurations. Overheads in a x.4 configuration will create a phantom center of the x.2 component while in an x.6 overhead configuration it will use the point source speakers. If you have a concern about a source in the overhead beds, try switching it to an object so you can have more control over how it renders.
- Depending upon the position and size metadata applied to an object, bed channels and objects can be sonically identical. For instance, an object placed in the left front with size set to zero will be identical to a left channel bed.